1. Field of the Invention
The invention relates to method and apparatus for exchanging a seal of a shock absorbing apparatus of a heavy moving object, particularly, an airplane.
2. Related Background Art
Generally, in an airplane, a shock absorbing apparatus called a shock strut is provided between the wheels and the body or wing portion in order to reduce shocks which are received upon landing and in the movement by wheels. The shock strut has an expandable elongated pillar shape having therein a cylinder and a piston. A gas and an oil are filled in the shock strut and a shock is reduced by a cooperating function thereof. Therefore, an O-ring type seal to seal the oil is provided for the shock strut. Such a seal must be exchanged when an oil leakage occurs.
A method of exchanging the seal of the shock strut which has conventionally been used will now be briefly explained with reference to FIG. 4. FIG. 4 is a diagram showing the exchanging work of the seal of the shock strut according to the conventional technique. In FIG. 4, shock struts 3 are coupled between a wing portion 1a and a body 1 of an airplane and wheels 2. As will be explained hereinafter, since the seal of the shock strut 3 is arranged between the cylinder and piston of the shock strut 3, the seal is exposed to the outside by extending the shock strut. Since the seal is the O-ring type seal, in order to exchange the seal, the wheels 2 and the shock strut 3 are disconnected and, after that, a new seal must be inserted from a gap between them. Consequently, as shown in FIG. 4, a plurality of large jacks 40 are installed below the body 1 and wing portion 1a of the airplane and the whole airplane is lifted up by the large jacks 40, thereby exposing the seals in the shock struts 3.
With such a conventional method, however, it takes time to install the large jacks 40, an advanced technique is required to lift up the airplane by the large jacks 40 while maintaining the airplane in the horizontal state, the jacks are deviated unless the certain supporting positions of the jacks are selected, and a long time and much labor are needed. There is also a problem regarding safety. In order to attach the O-ring type seal to the shock strut 3, it is necessary to elevate the shock strut and to insert the seal from the lower position. Therefore, hitherto, when the seal is exchanged, the shock strut is hung from the upper position by a rope or the like and the seal must be attached to a predetermined position from the lower position of the shock strut while going over the rope which hangs the shock strut, so that much labor is required. The leg portion of the shock strut has a slant surface which faces downward and it is undesirable to support the leg portion by the jack or the like from viewpoints of instability and safety of the procedure.
All airfields do not have the facilities such as large jacks. It is desirable, however, that the seals can be easily exchanged as necessary at any place.